Sailboat

ABSTRACT

A sail, suitable for use on a sailboat, iceboat or the like, comprising a number of vertically arranged, parallel, rigid strips. The cross-section of each strip has at least one curved side and is designed to produce the maximum lateral force when placed in the path of moving air. Mechanical means are provided to control the azimuthal orientation of all the strips with respect to the direction of air movement.

Unlted States Patent 1151 3,706,296 Milde, Jr. 1 1 Dec. 19, 1972 15 SAlLBOAT FOREIGN PATENTS OR APPLICATIONS [72] Inventor: Karl Milde, 198 Baltic 1,423,958 11/1965 France ..114/39 Brooklyn, NY. 11201 [22] Filed: July 28, 1970 Primary Examiner-Trygve M. Blix 21 A 1.N 58774 I 1 pp 0 [57] ABSTRACT [521 US. Cl .....114/102 A Sail Suitable for use a Sailboat 1939091 or the 51] Int. Cl. ..B6 3h 9/04 like, comprising number of vertically arranged [58] Field of Search ..114/39, 102, 103, 104 Parallel, rigid p The cross-section Of each Strip has at least one curved side and is designed to produce [56] References Cited the maximum lateral force when placed in the path of moving air. Mechanical means are provided to control UNITED STATES PATENTS the azimuthal orientation of all the strips with respect 3,403,653 10/1968 Bush ..114/103 to the direction of air movement. 1,504,057 8/1924 Koelkebeck... 14/103 3,295,487 l/1967 Smith ..'.,.114/39 X 11 Claims, 6 Drawing Figures PATENTED 19 I972 3, 706. 296

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INVENTOR.

F/G. 6 KARL F. MILDE, JR.

SAILBOAT BACKGROUND OF THE INVENTION reduced by increasing velocity of fluid flowing across the surface. Since the speed of moving air with respect to a sail is greater on the leeward than on the windward side thereof, there is a resultant force from windward to leeward..The existence of this resultant force maybe demonstrated, for example, on a catamaran sailboat which is capable of reaching speeds which are greater than would otherwise be theoretically possible.

Although a great deal of empirical and theoretical research has been devoted to the development of airfoils for use in aircraft, little or no consideration has been given to improving sails. This apparent absence of engineering activity is primarily due to the unique requirement of sails that they be quickly removable from their sailcraft in the event of a storm or when the craft is held at anchor or stored. Because of this requirement, it has been the practice to construct sails of a flexible material such as cloth.

SUMMARY OF THE INVENTION It is an object of the present invention, therefore, to provide a sail with a rigid airfoil which will increase the lateral force produced thereon when it is placed in the path of moving air.

It is a further object of the present invention to pro-' vide a rigid airfoil sail which may be quickly and easily extended into and removed from the path of moving air.

These objects, as well as other objects which will become apparent from the discussion that follows, are achieved, according to the present invention, by providing a sail in the form of a plurality of elongate rigid strips arranged vertically and in parallel. Each of these strips thus forms, in cross-section, an airfoil which should exhibit at least one curved edge to provide the desired increased thrust.

According to a preferred embodiment of the invention, the sail-strip is constructed with a moon-shaped cross-section to provide the maximum lateral thrust.

The plurality of sail-strips may be supported in their vertical and parallel position by any means known in the art. According to a preferred embodiment of the present invention, however, they are supported by flexible cables, chains or the like which extend horizontally and are attached to the opposite edges of each strip. These horizontal elements thus serve the dual purpose of supporting and controlling the azimuthal orientation of the sailstrips.

Due to the flexibility of the horizontal cables, chains or the like, the sail according to the present invention can be simply collapsed" against and secured to the mast of the sailcraft. Provided that the sail-strips and the horizontal supports are made of durable material, the collapsed sail need never be removed from the craft.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a representational diagram, partially cut away, of a sailboat provided with the Venetian blind type sail according to the present invention.

FIG. 2 is a representational diagram, in vertical view, of the sail shown in FIG. 1.

FIGS. 3a, 3b and 3c are cross-sectional views of typical airfoils which may be employed with sail-strips according to the present invention.

FIG. 4 is a detailed elevational view of a portion of a sail-strip employed in the embodiment of FIG. 1.

FIG. 5 is a cross-sectional view of the sail-strip and the supporting chains shown in FIG. 4.

FIGS. 6a and 6b are schematic diagrams showing possible orientations of sail-strips with respect to the direction of the wind.

- DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will now be described in connection with FIGS. 1 6 of the drawings.

FIGS. 1 and 2 show a sailboat 10 having arranged thereon a sail 12 attached to a mast 14. FIG. 1 shows the arrangement in elevation while FIG- 2 shows the sail and mast in bottom view.

The mast 14 is made rotatable about its axis. To this end, it is slidably supported by two guide openings 16 and 18 in the sailboat hull and is rested on a flat support member 20 at the bottom of the hull.

The mast 14 is provided with supports 22 and 24 extending from either side thereof at a number of points along its length. To each of these supports is attached a chain or flexible cable 26, 28, which extends horizontally rearward to a tension spring 30, 32 attached to a diagonal chain or cable 34. The diagonal chain or cable 34 extends from the top 36 of the mast 14 to a tension spring 38 that is anchored at its opposite end to a point 40 near the rear of the hull.

The horizontal supports 26 and 28 traverse and are attached to the outside edges of a plurality of vertically extending sail-strips 42. These sail-strips may thus be oriented, as, a group, by manually rotating the mast, preferably by means of some device (not shown) which provides mechanical advantage. Because of equalizing forces applied by the springs 30 and 32, the mast, upon release, will tend to return to the angular position illustrated with the sail-strips arranged perpendicular to the horizontal axis of the boat.

The sail-strips 42 may be further supported by chains or cables 44 extending horizontally from the mast 14 to further tension springs 46 connected to the diagonal 34. These additional chains or cables, which may be arranged on a common height with corresponding chains or cables 30 and 32, should pass through and be attached to the centers of the sail-strips 42.

As may be seen in FIG. I, the sail-strips may extend from a point below the gunwale of the boat to, or even above, the diagonal 34. Since the azimuthal orientation of the sail-strips may be controlled by rotating the mast, it is not necessary to provide a boom. In the absence of a boom, however, it will be necessary to provide a spinnaker-type sail for running before the wind.

The sail according to the present invention may also be arranged on a boom to provide additional flexibility and control and to permit the use of the sail as a source of thrust when running before the wind. In this case, the sail-strips 42 should extend downwardly merely to the boom. In addition, the spring 38 should be anchored to the rearward tip of the boominstead of to the point 4.0 at the rear of the hull.

It will be apparent that the sail according to the present invention and described above resembles a Venetian blind with vertical strips. Like a Venetian blind, the sail can be easily collapsed for storage or removal. If the spring 38 is disconnected from the anchor-point 40 on the hull of the boat, the sail-strips may be collected at, and fastened to the mast 14.

FIG. 3 illustrates three preferred embodiments of the cross-sectional configuration of the sail-strips according to the present invention. In each illustration the cross-section is oriented such that the mast would nor mally be positioned above the upper surface.

In FIG. 3a both surfaces of the sailstrip are curved and the sail-strip is of substantially constant thickness. Thissail-strip, which will thereforeclosely resemble the strip of a Venetian blind, may thus be made of sheet material.

Increased thrust may be obtained if the sail-strip is constructed as shown in FIG. 3b, with the upper but not the lower surface curved in shape. The increase in thickness at the center of the strip requires the air to travel a greater distance along the upper than along the lower surface. Since the air will accordingly move faster along the upper than along the lower surface, this airfoil will result in greater lateral thrust.

Still greater thrust may be obtained if the sail-strip is constructed with a moon-shaped cross-section as shown in FIG. 30. In addition to the increase in thrust obtainable from the greater thickness at the center than at the edges of the strip, this configuration serves to smoothly change the direction of motion of the air that passes along the lower surface. I

FIGS. 4 and 5 show in detail how chains 26, 28 and 44 may be attached to a sail-strip 42. As is best seen in FIG. 5, individual chain links may simply be passed through openings in the sail-strip 42.

FIG. 6 illustrates two examples of how the sail-strips according to the present invention may be oriented with respect to the wind. In FIG. 6a the sail-craft is on the port tack. The wind, indicated .by the arrow, impinges on the left side of the sail and is deflected rearward by the individual sail-strips.

In FIG. 6b the sail-craft is on the starboard tack. In this situation the edges of the sail-strips have been shifted (right edges shifted up and left edges shifted down) so that the wind will again be deflected rearward by the individual strips.

It should be noted that the arrangement of sail-strips in the sail according to the present invention has the advantage, over a single conventional sail, of controlling the flow of air as it passes over the succession of strips. In effect, each sail-strip acts as a jib for the sailstrip to its immediate rear as well as acting as a miniature mainsail and thus makes use of the well known slot effect.

As mentioned above, the principle advantage of the sail according to the present invention is an increase in thrust over sails of conventional design. This advantage is achieved without a loss of convenience; in fact, since the sail according to the present invention may be collapsed and stored against the'mast, the well known problems of removing, drying and folding fabric sails are entirely eliminated.

A secondary advantage of the sail according to the present invention is the possibility of constructing a sail-craft without a boom. Not only does such construction eliminate the well known hazards attendant the swinging of a boom, but it also permits the effective area of the sail to be extended downward to the gunwale of the craft.

It will be understood that the present invention is subject to such various changes, modifications and additions as will occur to those skilled in the art.

For example, although the sail-strips which are illustrated in FIGS. 2 and 6 are shown to have a lateral width which is slightly less than twice the horizontal spacing between successive strips, these strips may be constructed with either a lesser or greater width as the situation demands. If the strips are constructed with lesser width, the. resultant sail would be less efficient but easier to control; such a sail would be advantageous, for instance, for instructing inexperienced sailors. If the strips are constructed with greater width (and there is no theoretical upper limit to the possible width of a sail-strip), the sail would be more efficient but increasingly difficult to handle. Such a sail might be used, for instance, by experienced sailors to achieve increased speed in light winds.

It is therefore intended that the scope of the present invention be limited only by the following claims.

Iclaim:

1. A sailboat comprising, in combination:

a. a hull;

b. a sail having a plurality of rigid elongate strips arranged substantially vertically on said hull, said strips having two sides, two edges and two ends, one of said two sides forming a curved surface, the transverse cross-sections of said strips being substantially symmetrical about their central axes;-and

0. means for controlling the azimuthal orientation of said sail strips, said control means including a plurality of substantially horizontal first support means, attached to each edge of each of said strips at a plurality of points along said strips, for moving said edgesof each strip horizontally with respect to each other.

2. The sailboat defined in claim 1,.wherein said one side of one or more of said strips forms a curved surface and the other of said two sides forms a planar surface.

3. The sailboat defined .in claim 1, wherein each of said two sides of one or more of said strips forms a curved surface.

4. The sailboat defined in claim 1, wherein one or more of said strips are of substantially constant thickness.

5. The sailboat defined in claim 1, wherein one or more of said strips are substantially thicker at the central portion than at the edge portions thereof.

6. The sailboat defined in claim 1, wherein one or more of said strips have a substantially moon-shaped cross-section.

7. The sailboat defined in claim 1, further comprising a mast, arranged substantially vertically on said hull, said mast being rotatable about its axis, and wherein 10. The sailboat defined in claim 1, further comprising at least one second horizontal support means, attached to the horizontal centers of each of said strips, for maintaining said strips in proper alignment.

11. The sailboat defined in claim 1, wherein said first horizontal support means is flexible and wherein said control means further includes means for maintaining said first horizontal support means under tension when the sail is operative, whereby said strips may be collapsed together when the sail is not in use. 

1. A sailboat comprising, in combination: a. a hull; b. a sail having a plurality of rigid elongate strips arranged substantially vertically on said hull, said strips having two sides, two edges and two ends, one of said two sides forming a curved surface, the transverse cross-sections of said strips being substantially symmetrical about their central axes; and c. means for controlling the azimuthal orientation of said sail strips, said control means including a plurality of substantially horizontal first support means, attached to each edge of each of said strips at a plurality of points along said strips, for moving said edges of each strip horizontally with respect to each other.
 2. The sailboat defined in claim 1, wherein said one side of one or more of said strips forms a curved surface and the other of said two sides forms a planar surface.
 3. The sailboat defined in claim 1, wherein each of said two sides of one or more of said strips forms a curved surface.
 4. The sailboat defined in claim 1, wherein one or more of said strips are of substantially constant thickness.
 5. The sailboat defined in claim 1, wherein one or more of said strips are substantially thicker at the central portion than at the edge portions thereof.
 6. The sailboat defined in claim 1, wherein one or more of said strips have a substantially moon-shaped cross-section.
 7. The sailboat defined in claim 1, further comprising a mast, arranged substantially vertically on said hull, said mast being rotatable about its axis, and wherein said first horizontal support means are further attached to said mast, whereby the azimuthal orientation of said strips may be controlled by rotating said mast.
 8. The sailboat defined in claim 7, further comprising diagonal support means, attached to the top of said mast and extending diagonally downwardly, and wherein said first horizontal support means are further attached to said diagonal support means.
 9. The sail defined in claim 8, wherein said first horizontal support means are attached to said diagonal support means by means of tension springs.
 10. The sailboat defined in claim 1, further comprising at least one second horizontal support means, attached to the horizontal centers of each of said strips, for maintaining said strips in proper alignment.
 11. The sailboat defined in claim 1, wherein said first horizontal support means is flexible and wherein said control means further includes means for maintaining said first horizontal support means under tension when the sail is operative, whereby said strips may be collapsed together when the sail is not in use. 